New findings this year include: (1) adult male squirrel monkeys engage in vocal Aexchanges@ with adult females, but the loud calls typically used by the males are better suited for disrupting vocal exchanges between adult females (which use softer calls) than in establishing a communication link with the females. (2) in a study of the ontogeny of the most conspicuous vocalization in the common marmoset, a monogamous, sexually monomorphic primate, comparison of the vocal behavior of the same individuals at 3 and 12 months of age revealed that calling rate decreases with age, while call duration and peak frequency of individual call syllables increases with age. Both gender and individual differences were found even at 3 months of age, indicating that several messages can be encoded in the same call type in infant primates.(3) squirrel monkeys living in a Arain forest@ habitat in Florida under semi-free-ranging conditions engage in many of the same vocal communication patterns observed in our laboratory over many years in social groups of this species housed at the NIH Animal Center. This suggests that the communication patterns that we are able to study in great detail under controlled captive conditions are part of the natural vocal behavior of this species in the wild.